Calculators
Calculators, with the working shown
Every calculator on the site. Each shows its formula and every step of the working, runs in your browser, and computes with the same unit-tested functions as the accounting tools. Where a real set of books can answer, the ratio is also worked on Northwind Traders, the company the free course is taught on.
- Ratio calculators
- 29
- Glossary calculators
- 44
- Accounting tools
- 22
Liquidity and working capital
Can the company pay what falls due, and how long its cash is tied up.
- Current ratioCurrent assets ÷ Current liabilities
- Quick ratio(Cash and equivalents + Short-term investments + Accounts receivable) ÷ Current liabilities
- Cash ratioCash and equivalents ÷ Current liabilities
- Working capitalCurrent assets − Current liabilities
- DSO(Ending AR ÷ Credit sales for the period) × Days in the period
- DPO(Ending AP ÷ COGS for the period) × Days in the period
- DIO(Inventory ÷ COGS for the period) × Days in the period
- Cash conversion cycleDSO + DIO − DPO
- Inventory turnoverCOGS ÷ Average inventory
- Receivables turnoverCredit sales ÷ Average AR
- Collection effectiveness index(Opening AR + Credit sales − Closing total AR) ÷ (Opening AR + Credit sales − Closing current AR)
Leverage and coverage
How much debt it carries and how comfortably it services it.
Profitability and cash
How much of each dollar of revenue survives.
- EBITDANet income + interest + income taxes + D&A (≈ operating income + D&A with no other non-operating items)
- EBITNet income + Interest expense + Income tax expense
- Operating marginOperating income ÷ Revenue
- Net marginNet income ÷ Revenue
- Contribution margin(Revenue − Variable costs) ÷ Revenue
- Rule of 40Revenue growth % + EBITDA margin %
- Free cash flowOperating cash flow − Capital expenditures
Unit economics and recurring revenue
What a customer costs, what one is worth, and what is kept.
- CACSales & marketing spend ÷ new customers
- ARPAMRR ÷ Active customers, per month
- Customer lifetime value(ARPA × Gross margin) ÷ Revenue churn rate, both in the same period unit
- LTV to CACLTV:CAC is a unit-economics metric. It has no single agreed formula — state the inputs.
- Magic numberNet new ARR in the quarter ÷ prior-quarter S&M (equivalently (Δ quarterly revenue × 4) ÷ prior-quarter S&M)
- Logo churnCustomers lost ÷ starting customers
- Net new MRRNew + Expansion − Contraction − Churned
In the founder glossary
Calculators that sit inside the founder glossary, beside the term they compute: burn and runway, ARR, retention, ASC 606 allocation, Delaware franchise tax, SAFE conversion and more.
- Gross and net burn for a monthGross burn = Cash out · Net burn = Cash out − Cash in
- Months of runway and the month cash runs outRunway = Cash ÷ Net burn
- MRR and ARR from your customersMRR = Customers × Monthly price + Annual contracts ÷ 12 · ARR = MRR × 12
- Gross margin from your cost of revenueGross margin = (Revenue − Cost of revenue) ÷ Revenue
- Net and gross revenue retention for one cohortNRR = (Starting + Expansion − Contraction − Churn) ÷ Starting
- CAC and months to earn it backCAC payback = CAC ÷ (New MRR per customer × Gross margin)
- Burn multiple for a quarterBurn multiple = Net burn ÷ Net new ARR
- 13 weeks of cash, week by weekClosing cash = Opening cash + Receipts − Payments, rolled forward 13 weeks
- Post-money SAFE conversionOwnership = Investment ÷ Post-money cap · Price = lowest of cap, discount and round price
- Convertible note conversionShares = (Principal + Interest) ÷ lower of (Cap ÷ Shares, Round price × (1 − Discount))
- Priced round: price and dilutionPrice = Pre-money ÷ Pre-money shares · Post-money = Pre-money + Investment
- The option pool shuffleEffective pre-money = Pre-money − Pool % × Post-money
- Issued vs fully diluted ownershipFully diluted % = Holder's shares ÷ (Issued + Options + Unissued pool + SAFEs as converted)
- 83(b) deadline and the tax it movesDeadline = Transfer + 30 days (next business day if a weekend or DC holiday) · Income = FMV − Price paid
- QSBS: how much gain is excludedExcluded = Exclusion % × min(Gain, greater of $15M/$10M limit or 10 × basis)
- Is the strike at or above the 409A price?Spread = (FMV − Strike) × Options · Covered if grant ≤ valuation date + 12 months
- Deferred revenue scheduleMonthly revenue = Contract value ÷ Months · Deferred balance = Contract value − Revenue recognized
- Allocate the price across the promisesAllocated price = Transaction price × (Standalone price of the promise ÷ Sum of standalone prices)
- Prepaid expense scheduleMonthly expense = Amount paid ÷ Months covered · Prepaid balance = Amount paid − Expensed to date
- Capitalized commission amortizationMonthly amortization = Commission ÷ Benefit period in months
- Straight-line depreciationMonthly depreciation = (Cost − Salvage value) ÷ Useful life in months · Net book value = Cost − Accumulated depreciation
- Operating lease: liability, asset and expenseLease liability = Σ Payment ÷ (1 + r)^t, r = annual rate ÷ 12 · Lease cost = Total payments ÷ Months · ROU reduction = Lease cost − Interest
- Cash basis vs accrual basisCash basis: expense when paid · Accrual basis: Amount ÷ Months, each month it's used
- Economic nexus test and tax on a saleNexus if Sales > Dollar threshold or Transactions ≥ Transaction threshold · Tax = Price × Rate
- Delaware franchise tax, both methodsAuthorized shares: $175 to 5,000 shares, $250 to 10,000, +$85 per further 10,000 · Assumed par value capital: $400 per $1,000,000 (min $400) · Max $200,000 · Pay the lower, plus the $50 annual report fee
- Do I file a 1099-NEC for this contractor?File if total paid in the year ≥ threshold ($600 for payments in 2025 and earlier, $2,000 from 2026), unless exempt
- Federal corporate tax after an NOLNOL used = lesser of NOL and 80% × Taxable income · Tax = 21% × (Taxable income − NOL used)
- Stock option expense, straight-lineTotal cost = Grant-date fair value per option × Options · Monthly expense = Total cost ÷ Vesting months
- Allowance for credit losses by aging bucketRequired allowance = Σ (Receivables in bucket × Loss rate) · Expense = Required − Current allowance
- Break a Stripe payout back into its partsPayout = Charges − Refunds − Fees
- Remeasure a foreign-currency balanceGain or loss = Foreign balance × Month-end rate − Foreign balance × Booked rate
- R&D credit, alternative simplified methodCredit = 14% × (QREs − 50% × average of 3 prior years), or 6% × QREs with no history · Payroll offset ≤ $500,000
- Section 174A: what you deduct this yearDomestic: deducted in full · Foreign: ÷ 15 years from mid-year (1/30 in year 1)
- A federal tax provision, current and deferredTax expense = Current tax + (Opening − Closing net deferred tax asset) · Deferred tax = 21% × (NOL + Temporary differences) − Allowance
- Days sales outstanding and the cash it ties upDSO = Average receivables ÷ Revenue on credit × Days in the period
- Days payable outstandingDPO = Average payables ÷ Cost of revenue × Days in the period
- Retained earnings roll-forwardClosing = Opening + Adjustments + Net income − Dividends
- Is this error material? A first screenSize = |Error| ÷ |Pretax income|, against SAB 99's 5% rule of thumb · plus the qualitative factors
- Does the trial balance balance?Debits (assets + expenses) = Credits (liabilities + equity + revenue)
- Capitalized software: asset and amortizationCapitalized = Development cost × Qualifying share · Monthly amortization = Capitalized ÷ Useful life
- Using an NOL, with and without a §382 limitNOL used = lesser of 80% × taxable income and, after an ownership change, Value × long-term tax-exempt rate
- Who gets what at an exitPreferred = greater of (Preference [+ participation]) and Ownership × Proceeds · Common = Proceeds − Preferred
- Gross revenue retention for one cohortGRR = (Starting − Contraction − Churn) ÷ Starting
- Tying a 1099-K to your booksNet sales = Gross − Sales tax − Refunds − Chargebacks · Deposits = Gross − Refunds − Chargebacks − Fees
Accounting tools
The accountant's toolbelt: schedules, reconciliation and checks. The same definitions run in the Chrome extension.
- Difference diagnoserOut by 8,100? That is divisible by 9 — a transposition. This says which error fits the gap.
- Which invoices make this deposit?A deposit against forty open items. Exact subset-sum over minor units — no floating point.
- Two-list matcherBank against ledger: exact, then reference, then a date window, then one-to-many — and what is left on both sides.
- Duplicate paymentsSame vendor, same amount, close in time — plus the same reference whatever the date.
- Benford & round numbersTwo cheap tests over a pasted column. Neither proves anything; both tell you where to look.
- Depreciation scheduleStraight-line, declining balance or SYD, with the convention that decides the first period.
- Prepaid & deferred releaseA premium paid on the 17th does not release in twelve equal slices. Day-weighted, or even — your call.
- Loan amortisationLevel payment solved, then walked in minor units so the last payment clears the balance exactly.
- Lease — ASC 842 / IFRS 16PV of the payments at your IBR, the liability unwind and the ROU asset — straight-line for a finance lease, the plug to a level cost for an operating one.
- VAT / sales taxGross to net is a division, not a multiplication. The three figures always add back up.
- Margin & markupThey are not the same number, and confusing them is how a price list quietly loses money.
- FX conversion & gain/lossThe rate is the one in your policy, so you type it. No live rate, no network call, no stale surprise.
- Penny-exact allocationSplit 100.00 three ways and get 33.34 / 33.33 / 33.33 — never a cent left in suspense.
- NPV, IRR & XIRRIRR by bisection, so a sign-change-heavy series does not converge on a confident wrong answer.
- Effective vs nominal rate12% compounded monthly is 12.68%. That difference is the covenant you either pass or fail.
- Payment terms & due dates2/10 net 30 is borrowing at 37% a year. This tells you whether to take the discount.
- Day count & proration30/360 is wrong about the calendar and right about the contract. Both are here.
- Journal entry balancerPaste an entry, see the out-of-balance, and copy an import-ready CSV.
- Trial balance checkerBalances — and then the harder question: is anything sitting on the wrong side of its normal?
- Number cleaner(1,234.56) · 1.234,56 · 1,234.56- · $ 1 234.56 · 1.2k → clean signed values, one per line.
- IBAN, routing, VAT, EINChecksums, offline. A valid IBAN is not a real account, and this says so.
- Amount in wordsFor the check, the note, the contract schedule — with the cents as a fraction over 100.